1. Field of the Invention
This invention relates to the field of integrated circuit chip packaging, and more specifically to devices for connecting an integrated circuit chip to a printed circuit board.
2. Description of Prior Art
Integrated circuit chips have a large number of pins that must be connected to a circuit board. The circuit board sends and receives signals from the integrated circuit chip and also provides power and ground for the chip. Integrated circuit chips are small in comparison to circuit boards and typically have pins that are separated by 100 μm to 200 μm. The circuit boards to which integrated circuit chips are connected have connector pads that typically are separated by no less than approximately 1 mm.
It is necessary to provide means for connecting the closely-spaced contacts of integrated circuit chips to the more widely-spaced contacts of a circuit board. The connections between the chip and the printed circuit board include ground, power and signal. To maintain separation between signal paths, typical architecture requires one or more signal layers, separated from each other by one or more power planes or ground planes to reduce signal interference. Signal, ground and power layers are electrically isolated from each other by interposed layers of dielectric. Typical redistribution packages comprise closely-spaced contacts that match the contacts of an integrated circuit chip and communicate electrically with the traces on the otherwise isolated signal layers, ground layers and power layers by vias. The traces on different signal, ground and power layers are connected to traces on respective other signal, ground and power layers through the use of vias that provide electrical communication between otherwise isolated layers. The signal, ground and power layers are also connected by vias to more widely-spaced contacts of the redistribution package that communicate with contacts on the circuit board.
Signal vias, however, can generate “cavity noise” that results from the interruption of displacement current whenever switching activity occurs thereon. In addition, these prior art coplanar redistribution packages often suffer from signal noise due to signal coupling.
3. Objects and Advantages
It is therefore a principal object and advantage of the present invention to provide a redistribution package that permits connection of a chip to a printed circuit board without generating cavity noise.
It is an additional object and advantage of the present invention to provide a redistribution package that does not utilize signal vias.
It is a further object and advantage of the present invention to provide a redistribution package that diminishes the likelihood of noise coupling in the package.
Other objects and advantages of the present invention will in part be obvious, and in part appear hereinafter.